Grinding balls.



' PATE'NTED OCT. 22. 1907.

G. HOFFMANN. GRINDING BALLS. APPLICATION FILED JUNE 5; 1907.

UNITED PATENT OFFICE.

GRINDING BALLS.

a part hereof.

The grinding of metal balls for ball bearings and other purposes for which accuracy, uniformity and high finish are desirable, is commonly effected in amachine which comprises two disk-like plates of metal, relatively rotatable and pressed yieldiugly, one toward the other, concentric grooves being formed in the, adjacent faces of the plates or in the face of one of them in which the balls are received together with an abrasive powder,

usually emery powder, mixed with oil. The periphoral speed of balls in such machines is not the same as tho pcripherafspeed of the portionsoi the plate or plates against which they are pressed, so that the loose partirdes of abrasive material between the balls and such portioils of the plates are in this manner enabled to act upouthe surfaces of the balls. The portion of the ball which is thus removed by a par 310 of the abrasive material is almost'iulinitesimal, but each particle of abrasivemater-inl nevertheless makes upon the surface of the ball a scratch, the clutracter of which is dependent upon the size and character of the particle. The whole surface of 'thc finished ball, therefore, is made up of a vast number of scratches which are sometimes yisible to the naked eye as a sort'of cloudiness or dullness upon the surface of the ball and are always plainly apparent when the ball is examined with a mi croscope of moderate power. The balls finished in this manner therefore leave something to be desired in the way of smoothness and by the present invention it has been discovered that a much greater approach to per foot smoothness of surfamr, as well as almost mathematically perfect spherir-ity and accuracy of the balls can be secured by dispensing alLogetherwith the use of loose abrasive material and by carrying on the grinding between two 'disks or plates, relatively rotatable and one or the other provided with concentric grooves as before, while one of such disks or plates is itself com posed of abrasive material. Especially good results are attained if such particles of abrasive material as i may be loosened from the plate or disk as it wears away are immediately removed, as by washing them out with a constant and ampleflow of a suitable liquid.

The invention will be more fully explained hereinafter with reference to the accompanying drawing in which is represented so much of a grinding machine as is necessary to enable the invention to be understood and in which i r 5 Figure 1 is a view in side elevation, partly broken i Specification of Letters Patent. Application filed June 5,1907. Serial No. 377.316.

Patented Oct. 22, 1910?.

out, of a portion of-such a machine, and Fig. 2 is a top view of the same.

In the particular form (if mechanism which is chosen for illustration of the nature of the invention a station my disk A, prcferablypf metal and having in its working face a series of concentric grooves a, is mounted upon a stationary shaft B, being held from rotation thereon and also from'longitudinal movement by anysuitabie means, such as a pin b passing through the hub of the grinding disk or plate A and the shaft and remoyable to permit the disk or plate to be moved back upon the shaft when necessary. A rotating disk or plate made of any suitable abrasive material, such as corunrlum, for

example, is mounted to rotate upon the shaft 13, being provided for this purpose, in the machineshown, with a suitable wheel or belt pulley D. It is pressed toward the plate or disk A by any suitable. means, as a stiff v spiral spring E surrounding the shaft 13 and abutting against an adjustable nut e. The plate or disk C may or may not be provided, when new, with concentric grooves in its working face, which correspond to the grooves (z. in the working face of the dlsk or plate A, but such grooves are naturally formed therein as he use of the machinecontinues and are necessary to tiny proper action upon the balls, which depends upon the" different; peripheral speeds of different portions of the balls in contact with the sides of the grooves.

The balls to be ground, which are shown in pl. o in Fig 1, may be introduced and removed and interchanged through slots in the disk A and by means of a table G in spiral form, all as fully explained in'lietters Patent of the United States No, 803,164, datedOctober 31, 1905, or by any other suitable means. The operation of the machine shown in the drawing is in general the same asthat of the machine described in said Letters Patent, but no emery powder or other loose abrasive material is supplied to the machine, the abrasive action of the disk 0 being alone reliedupon. If this disk isrnadc of suitable material, 'it will slowly wear away in an impalpable powder, but to prevent any scratching of the balls by particles which may be loos ened from the diit is desirable that they be removed immediately. If the ;rinding, should be done dry, such loose particles would be quickly thrown out or might be blown out by a blast of air suitably directed. The grinding, however, is preferably carriedon with a suitable liquid, kerosene oil. being found to be well adapted for the purpose, and in order that all loose par ticles of abrasive material may be immediately re moved, a somewhat copious flow oi'the liquid is main 'tained throughout the operation.

As shown in the drawing the working parts of the machine are mounted over a tank or reservoir H into which through a pipe h to a centrifugal pump 1 by From the tank H the'oil flows which it is returned to the grinding disks through a pipe i by whine-the oil or other liquid is distributed upon the.

are precipitated.

table G from which it passes with the balls through the disk A to the grinding surfaces. By such means the particles of metal and of abrasive material are immediately removed from the grinding surfaces and the scratching of the balls thereby is wholly obviated While the machine herein shown is well adapted for carrying out the invention. it will, nevertheless. be un derstood that the invention is not restricted to any particular form or type -t' machine and tlmtithe mechanism shown and dscribed herein can be varied as may be 1-. A machine for grindiin; halls compril a metal the balls having concentric grooves adapted to recu e l l l l and a disk of abrasive material, alsohaving concentric. grooves in its working face adapted to receiving the balls therein one of said disks being rotated with respect to the other. i

-l. A machine for arinding balls comprising two relatively rotating disks having parallel working faces with concentric grooves therein adapted to receive the balls be tween them, one ot said disks being formed 01' abrasive material. and means to remove immediately the loosened abrasive material,

.3. machine for grinding balls comprising two relatively rotatini: disks having parallelavorking faces with concentric grooves therein adapted to receive the balls between them. one or said disks being formed of abrasive material. and means to discharge a'stream of liquid between the di 'ks throughout the operation to wash out the loosened particles of abrasive material.

t;. machine for grinding balls comprising two relatively rotated disks having parallel working faces with concentric crooves therein adapted to receive the-halls tt-ureen them one of said disks being formed of abrasive material. a pump, connections to discharge liquid from the pump upon the working t'aces ot the disks to wash out the loosened particles of abrasive material, a tank to receive. the liquid from the disks, and connections to return the liquid from the tank to the pump.

This specification sinned and witnessed this 3d day of June. A. 1).. 19417.

l-lliNS'l til'SiAV HOFFMANN.

In the presence of l'him J. hut Animosu l, 0 Sum. 

